Through the analytical framework of ‘transnational constitutional engagement’, this article examines the dynamically developing practices of the South Korean Constitutional Court as it engages with international and foreign elements, both within and beyond constitutional adjudication processes. Diverse underlying factors and orientations in varied contexts, and the complex interactions between them, are responsible for shaping the modes of a local constitutional actor’s engagement with the transnational. In the vertical aspect, the court adopts international human rights law as a substantive standard of constitutional review through a version of cosmopolitan constitutional interpretation, while it has nevertheless exhibited ambiguity and incoherency in concrete applications. The horizontal aspects of transnational engagement include the court’s practice of referencing foreign law and cases in constitutional adjudication. The vibrancy and the evolving patterns of its citation practice reflect the court’s growing self-perception vis-à-vis the world – although limitations remain, such as geographical asymmetries among referenced jurisdictions. The court has also been enthusiastic in interacting with various transnational counterparts beyond adjudication processes, demonstrating eminent leadership in regional network-building among constitutional courts in Asia. With both cosmopolitan aspirations and nationalist ambitions playing a role in their shaping, the modes of transnational constitutional engagement are not to be generalized, but require contextualization, and the relevant practices should be subject to constant evaluations for their contribution in producing sound and effective concretizations of the values of global constitutionalism.